Circuit module fan assembly

ABSTRACT

An electronic circuit module fan assembly is disclosed including a circuit module housing, circuit modules, and a fan module. The fan module has a fan unit for cooling the circuit modules. The fan module can be mounted in the housing interchangeably with the circuit modules. The fan module has time delay circuitry for delaying the time when the fan module is powered up until after the initial power surge of the electronic system. The fan module also has noise filter circuitry. A fan module is disclosed wherein the fan unit is slidably attached to the fan module to allow the fan to be placed in different positions for cooling purposes. The fan module can be constructed so that the fan unit is interchangeable with a panel having circuitry.

This is a continuation of the application Ser. No. 771,154, filed Oct.3, 1991, now U.S. Pat. No. 5,191,230, which was a continuation ofapplication Ser. No. 303,642, filed Jan. 30, 1989, that issued in U.S.Pat. No. 5,079,438.

BACKGROUND

The field of the present invention is air cooling systems withinelectronic systems. More particularly, the present invention relates toa fan assembly for use in an electronic system with circuit modules.

Electronic systems, such as computers, employing modular constructionare common. A typical electronic system includes a plurality of circuitmodules mounted within a housing. The circuit modules can be easilyinserted or removed for replacement or repair. The modular constructioncontributes to the compactness of the electronic system.

A plurality of modular integrated circuits or chips are typicallymounted on each circuit module of current electronic systems. As largescale integration technology has improved, the circuitry per unit areawithin a modular integrated circuit has increased dramatically. Thenumber of modular integrated circuits which can be packed on a circuitmodule has also increased. Unfortunately, this increase in thecompactness of electronic circuitry has also resulted in an increase inthe heat generated per unit area of the circuitry. Therefore,overheating of the numerous chips on circuit modules has presented aserious problem.

To overcome this problem, most electronic systems employ the use of aircooling systems in conjunction with heat sink devices. Typically, airflow from a fan is directed past heat sink devices which are thermallyconnected to the circuitry on the circuit boards. An example of such adevice is illustrated in U.S. Pat. No. 4,122,508 to Rumbaugh. In themodular circuit board assembly disclosed in U.S. Pat. No. 4,122,508, ablower 30 is located in a side panel of the housing 11. The air flowfrom the blower 30 is directed past heat sinks 19 which are thermallyconnected to circuit boards 16.

The fan in current electronic systems is usually remote from most of thecircuit modules within the electronic system housing. The modularintegrated circuits on the circuit modules most remote from the fanreceive the least amount of cooling effect because the cooling airabsorbs heat as it passes the circuit modules in closer proximity to thefan. In many electronic systems, this problem is exacerbated because thecircuit modules which generate the most heat are often required by thephysical constraints of the electronic system to be located most remotefrom the fan. As a result, heat sinks are used to dissipate heat fromthe integrated circuits more rapidly than would otherwise be possible.However, heat sinks decrease the compactness of the electronic systemand increase the cost and complexity of manufacturing the electronicsystem.

An additional problem arises from the remoteness of the fan from many ofthe circuit modules within the electronic system. Due to the nature ofsome system housings, the circuit modules themselves often block thecooling air flow of the fan from reaching the other circuit modules.

A further problem is that modular electronic systems typically havespecial compartments within the electronic system for housing the fan,thus contributing to expense in the manufacture of the electronicsystem. A further problem resulting from such compartments is usage ofthe limited available space within most electronic systems. The specialconstruction of fan compartments further increases the difficulty ofremoving the fan for maintenance or replacement.

SUMMARY

The present invention solves the foregoing problems. The presentinvention is an electronic circuit module fan assembly for an electronicsystem which provides more direct air turbulence on the circuit modulesthereby dissipating heat more rapidly and reducing the need for heatsinks. The present invention also provides a more compact, a lesscomplex, and a lower cost cooling system.

The electronic circuit module fan assembly of the present inventioncomprises at least one circuit module and a fan module within anelectronic system. The assembly can also include a circuit modulehousing. The circuit module housing has receiving means for receivablymounting circuit boards. The circuit module has circuitry and is mountedon the receiving means of the housing.

The fan module has a mounting structure which can be a base board, amounting means for mounting the fan module in the electronic system, atleast one electric fan unit, and a driving circuit which is electricallyconnected to the fan unit. The mounting means is for mounting the fanmodule in the electronic system interchangeably with the circuitmodules. The electric fan unit is mounted to the mounting structure sothat there is space between the fan unit and the circuit modules to becooled when the fan module is installed in the electronic system. Thedriving circuit is for selectively activating the fan unit. The fan unitcreates air turbulence near the circuit module to cool the circuitry ofthe circuit module when the driving circuit is activated.

The driving circuit can receive power from the same power source as thecircuit board and can have a time delay means for delaying the time whenthe fan unit is activated after the electronic system is powered on. Thedriving circuit can further include a noise filter for filtering powertransients. The fan module can have a mechanical switch for manuallyselectively activating the fan unit.

The present invention can also include a light-indicator device forindicating that the electronic system power is on. The fan module of thepresent invention can further be constructed so that the fan unit isremovable and replaceable with modular integrated circuitry.

The present invention also includes a fan module for an electronicsystem. The fan module has essentially the same features as the fanmodule of the electronic circuit module fan assembly set forth above.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with reference to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 is a perspective view of an electronic circuit module fanassembly of the present invention;

FIG. 2 is a front elevation view of a fan module according to thepresent invention;

FIG. 3 is a front elevation view of a fan module according to a secondembodiment of the present invention; and

FIG. 4 is a front elevation view of a fan module wherein the fan unit isremoved and replaced with a panel having circuitry.

DESCRIPTION

Referring to FIGS. 1 and 2, an electronic circuit module fan assembly 10comprises a circuit module housing 12, circuit modules 14, and a fanmodule 16. The electronic circuit fan assembly 10 is part of a largerelectronic system, such as a computer system.

Each circuit module 14 comprises a circuit module base board 18, anarray (indicated by the vertical and horizontal double lines 22) ofmodular integrated circuits 20, and circuit module mounting means 24 formounting the circuit module 14 on the side wall 26 of the housing 12.The modular integrated circuits 20 are mounted in rows on the base board18. The side wall 26 functions as a receiving means for receivablymounting circuit modules 14 and fan modules 16 on the housing 12. Thefan module 16 comprises a fan module mounting structure including a baseboard 28. The fan module 16 further comprises a fan unit 30, fan powerwires 32, a driving circuit 34, a light-indicator circuit 36, and fanmodule mounting means 38 for mounting the fan module 16 on the side wall26. The fan module mounting means 38 is mounted to the base board 28 bymounting bolts 42. The circuit module mounting means 24 and the fanmodule mounting means 38 are of identical construction so the circuitmodules and fan modules are interchangeable. However, the fan module 16and the circuit modules 14 can have mounting means of differentconstruction, as long as the fan module fits into the same space andmounts to the same receiving means as the circuit modules 14.

The fan unit 30 is mounted to the fan module base board 28 by fan bolts40. Therefore, the fan unit 30 is easily removed from the base board 28.In some embodiments of the invention, the mounting structure for the fanunit 30 is not a base board 28. For example, the mounting structure canbe a frame with fan module mounting means 38 for mounting the frame tothe housing 12. Also, a fan housing can be provided around the fan unit30 to prevent interference with electronic signals to or from theelectronic system.

The base board 28 of the fan module 16 can have modular integratedcircuits mounted on the portion of the base board 28 which does not havethe fan unit 30. In addition to modular integrated circuits, otherelectronic components, such as components for telephone communicationequipment can be included.

The fan module 28 is electrically connected to the power source of theelectronic system by the board connector 60. The board connector 60inserts into the receiving connectors 61 attached to the housing 12. Insome electronic systems, the board connector 60 serves as the fan modulemounting means for mounting the base board 28 to the housing 12 becausebrackets 44, 46, and 48 are not included. The receiving connectors 61function as electrical connections between the board connectors 60 ofthe modules 14 and 28 and the electronic system. The receivingconnectors 61 can also serve as the mechanical receiving means forreceivably mounting the circuit modules 14 and the fan module 28 on thehousing 12.

The mounting means 38 comprises upper and lower board brackets 44 and46, respectively, and L-bracket 48. The upper and lower board brackets44 are attached to the L-bracket 48 by conventional means, such asrivets or welding. Alternatively, the upper and lower board brackets 44and 46 can be adapted to fit into slots within the L-bracket 48 for easyinstallation and removal. The L-bracket 48 is connected to the receivingmeans by a housing bolt 50. The fan power wires 32 are connected to theboard traces 55 by conventional electrical connectors.

The fan module 16, and in particular the driving circuit 34, receivesits power from the power source of the electronic system. The drivingcircuit 34 has a time delay means for ensuring that the fan units willnot be powered on at the same time as the other component parts of theelectronic system, such as the circuit modules 14. When the electronicsystem is powered on, many component parts of the electronic system drawcurrent from the system power supply. The time delay means causes thefans to power up after the initial power surge in the electronic systemis over. For many electronic systems a time delay of approximately oneto two seconds is sufficient.

FIGS. 1 and 2 show only one fan unit 30 mounted on a first planarsurface 54 of the fan module base board 28. However, a second fan unitcould be mounted in the sector 56 on the first planar surface 54. Also,additional fan units could be mounted on the second planar surface 58 Ofthe base board 28. Opposite the first planar surface 54. The fan unitscan be mounted at selected positions along the planar surface of thebase board 28. Finally, as is illustrated in FIG. 4, it is possible toconstruct the fan module 16 so that the fan unit 30 can be removed andreplaced with a panel 92 having modular integrated circuitry, as on thecircuit modules 14.

The fan unit 30 has a height and width to fit on the base board 28without protruding beyond the edges of the base board 28. The depth orthickness of the fan unit 30 is such that space is left between the fanmodule 16 and the circuit modules 14 so cooling air can flow easily. Thedepth of the fan unit 30 is usually on the planar surface of the baseboard 28 opposite to the circuit module to be cooled.

The time delay portion of the driving circuit 34 is illustrated in FIG.2. The dotted lines represent electrical traces 55 in the base board 28.The time delay portion of the driving circuit 34 includes an input 62from a 12 V power source of the electronic system, a 1 K ohm resistor64, a base capacitor 66, an emitter capacitor 68, and a transistor 70.The 12 V input 62, the 1 K ohm resistor 64, and the base capacitor 66are electrically connected in series to ground 72. The input terminal ofthe resistor 64 is connected to the collector of the transistor 70 andthe output terminal of the resistor 64 is connected to the base of thetransistor 70. The emitter of the transistor 70 is connected to theemitter capacitor 68. Both the emitter capacitor 68 and the basecapacitor 66 can be 220 μf. The emitter capacitor 68 is connected toground and thus can function as a noise filter to filter transients fromthe power source of the electronic system.

A mechanical switch 74 is provided so the fan unit 30 can be manuallyswitched to the on and off states. If a fan unit is provided in sector56, a similar mechanical switch can be provided.

The light-indicator circuit 36 comprises a 5 V input 76 from theelectronic system, a 220 ohm resistor 78, and an indicator light 80, allin series. The indicator light 80 is connected to ground 72. Otherlight-indicator circuits well known to those skilled in the art can beprovided.

The air flow created by the fan unit 30 during operation is initiallydirectly through an opening behind the fan unit 30 and against theadjacent circuit module 14 along the arrow 82. The air then tends to bedirected along the surface of the circuit module 14 away from the areaof the fan unit 30. A switch can be provided on the fan unit 30 so thedirection of the air flow can be changed by changing the rotationaldirection of the fan blades. In some embodiments of the invention,channels can be provided between the circuit modules 14 and the housing12 so that air can more easily flow throughout the housing 12. Finally,air vents can be provided in the housing 12 to take in cool air and letout heated air.

Turning to FIG. 3, another embodiment of fan module 83 is illustratedwherein the fan unit 30 is slidable on a set of racks 84 and 86. The fanunit is attached to the racks 84 and 86 by slidable connectors 88. Theslidable connectors 88 are attached to the fan unit 30 by connectorbolts 90. The slidable connectors 88 slide along the racks 84 and 86 sothat the fan unit 30 can be positioned at various locations along theopening 89 to cool circuitry at selected locations on an adjacentcircuit module. The driving circuitry is the same as that of FIG. 2 andcan be electrically connected to the fan unit by fan wires 91 or byother suitable means well known to those skilled in the art.

FIG. 4 illustrates a fan module 93 on which the fan unit is removed andreplaced with a modular integrated circuit panel 92. The circuit panel92 is electrically connected to the electronic system through the fabricconnector 94. In this way, the individual modular integrated circuits 96can function in the same way within the electronic system as they do ona circuit module. The fan module 93 on which a panel 92 can be mountedis advantageous in that the module can selectively function as a coolingunit or mounting structure for circuitry. The driving circuit 34 on thefan module 93 can be the same as that on the fan module 61 of FIG. 2.The driving circuit 34 is electrically connected when the circuit panel92 is replaced by a fan unit 30.

The electronic circuit module fan assembly of the present invention hasmany advantages. The fan module of the present invention can be locateddirectly adjacent to the circuit module to be cooled. The presentinvention provides more direct air turbulence for cooling of thecircuitry than prior cooling systems. The cool air from the fan unit ofthe present invention displaces the warming air in closest proximity tothe circuit module. Thereby preventing the circuit module from gettinghot. In prior cooling systems, the fans are typically located remotelyfrom at least some of the circuit modules in the electronic system. Theproximity of the fan to the circuit modules can also serve to preventdust or other particles from accumulating on the circuit modules ortheir circuitry.

The electronic circuit module fan assembly of the present invention alsoprovides a more compact cooling system because a separate compartmentfor the fan apparatus is not required. Prior cooling systems typicallylocate the fan within a separate cabinet in the housing, resulting inmore complicated and expensive manufacture of the electronic system andthe usage of limited space in the electronic system. An additionaladvantage of the present invention is that the number of fans used inthe cooling system can be varied without major alterations in theelectronic system. The fan modules can be removed or added according tothe needs of the user of the electronic system. If fan modules areremoved, there is more room for additional circuit modules to beinstalled.

The present invention further provides for ease of removal of the fanmodules for maintenance and replacement. One of the advantages ofelectronic systems having circuit modules is ease of maintenance andreplacement of the circuit modules. The present invention takesadvantage of this modular construction in relation to the coolingsystem. A further advantage of the present invention is that it can beeasily adapted to draw current from the power source of the electronicsystem. Moreover, the close proximity of the fan units of the presentinvention to the circuit modules allows for the employment of fans whichdraw less power. In prior cooling systems, the remoteness of the fansfrom the circuit modules often requires fans with high capacity airflows. The proximity of the fans to the circuit modules being cooledalso allows for fans with a more compact size and lower cost andcomplexity.

Finally, the present invention substantially reduces the need for bulkyand elaborate heat sinks in thermal connection with the circuitry on thecircuit modules. The reason for this is that the air turbulence providedby the fans of the present invention more directly cools the circuitmodules.

Although various embodiments of the present invention have beendescribed in considerable detail, other versions and embodiments of theinvention are possible. Therefore, the present invention is not limitedto the embodiments described herein, but instead is defined by thespirit and scope of the appended claims.

What is claimed is:
 1. A fan module for cooling a circuit module in anelectronic system,wherein the circuit module includes:(i) a circuitmodule base board; (ii) circuitry mounted to the circuit module baseboard; and (iii) a circuit module board connector attached to thecircuit module base board; and wherein the electronic system includes anelectrical circuit for providing electrical power to the electronicsystem, and a plurality of electrical connectors each for: (1)electrically connecting the circuitry to the electrical circuit in theelectronic system, and (2) mechanically connecting the circuit modulebase board to the electronic system by the circuit module boardconnector; the fan module comprising:(a) a fan module base board havingfirst and second planar surfaces and an edge; (b) an electrical fan unitmounted to the first planar surface of the fan module base board forcooling the circuitry mounted to the circuit module base board; (c) adriving circuit for electrically connecting the electrical circuit tothe fan unit and for activating the fan unit when the fan module ismounted to the electronic system and the electronic system is poweredon; and (d) a fan module base board connector attached to the fan modulebase board for mechanically mounting the fan module base board to eachof the electrical connectors interchangeably with the circuit modulebase board, the fan unit having a depth such that the fan unit is spacedapart from the circuitry on the circuit module when the circuit moduleand the fan module are mounted to different ones of the electricalconnectors.
 2. The fan module of claim 1 wherein (1) the electronicsystem further includes a housing, (2) the circuit module furtherincludes a circuit module bracket assembly attached to the circuitmodule base board and attachable to the housing, and (3) the fan modulefurther includes a fan module bracket assembly attached to the edge ofthe fan module base board and attachable to the housing interchangeablywith the circuit module bracket assembly.
 3. The fan module of claim 1wherein the electrical connectors are receiving connectors foroptionally receiving the circuit module board connector and the fanmodule board connector.
 4. The fan module of claim 1 wherein the drivingcircuit has a noise filter for filtering power transients on the drivingcircuit.
 5. The fan module of claim 1 wherein the fan unit isselectively mountable on the first and second planar surfaces of the fanmodule base board.
 6. A fan module for cooling a circuit module in anelectronic system,wherein the circuit module includes:(i) a circuitmodule base board; (ii) circuitry mounted to the circuit module baseboard; and (iii) a circuit module board connector attached to thecircuit module base board; and (iv) a circuit module bracket assemblyattached to the circuit module base board and attachable to a housing ofthe electronic system; and wherein the electronic system includes thehousing, an electrical circuit for providing electrical power to theelectronic system, and a plurality of electrical connectors each for:(1) electrically connecting the circuitry to the electrical circuit inthe electronic system, and (2) mechanically connecting the circuitmodule base board to the electronic system by the circuit module boardconnector; the fan module comprising:(a) a fan module base board havingfirst and second planar surfaces and first and second edges; (b) anelectrical fan unit mounted to the first planar surface of the fanmodule base board for cooling the circuitry mounted to the circuitmodule base board; (c) a driving circuit for electrically connecting theelectrical circuit to the fan unit and for activating the fan unit whenthe fan module is mounted to the electronic system and the electronicsystem is powered on; (d) a fan module base board connector attached tothe fan module base board adjacent the first edge for mechanicallymounting the fan module base board to each of the electrical connectorsinterchangeably with the circuit module base board; and (e) a fan modulebracket assembly attached to the second edge of the fan module baseboard and attachable to the housing, the fan unit having a depth suchthat the fan unit is spaced apart from the circuitry on the circuitmodule when the circuit module and the fan module are mounted todifferent ones of the receiving connectors.
 7. The fan module of claim 6wherein the electrical connectors are receiving connectors foroptionally receiving the circuit module board connector and the fanmodule board connector.
 8. The fan module of claim 6 wherein the fanmodule base board has an opening behind the fan unit through which anair flow is directed when the fan unit is operating.
 9. The fan moduleof claim 6 further including a light-indicator device for indicating thepower for the electronic system is on.
 10. The fan module of claim 6wherein the electrical connectors comprise substantially parallel slotsin spaced apart relation to one another and wherein the circuit moduleboard connector and the fan module board connector each comprise aprotruding portion of the respective base boards, each protrudingportion being capable of fitting snugly in any one of the slots.
 11. Afan module for cooling a circuit module in an electronic system,whereinthe circuit module includes:(i) a circuit module base board; (ii)circuitry mounted to the circuit module base board; and (iii) a circuitmodule board connector attached to the circuit module base board; andwherein the electronic system includes an electrical circuit and aplurality of electrical connectors each for (1) electrically connectingthe circuitry to the electrical circuit in the electronic system, and(2) mechanically connecting the circuit module base board to theelectronic system by the circuit module board connector; the fan modulecomprising:(a) a fan module base board having first and second planarsurfaces and an edge; (b) an electrical fan unit mounted to the firstplanar surface of the fan module base board for cooling the circuitrymounted to the circuit module base board; (c) a driving circuit forelectrically connected to the fan unit and for activating the fan unitwhen the fan module is mounted to the electronic system and theelectronic system is powered on; and (d) a fan module base boardconnector attached to the fan module base board for mechanicallymounting the fan module base board to each of the electrical connectorsinterchangeably with the circuit module base board and for electricallyconnecting the driving circuit to the electrical circuit through one ofthe electrical connectors, the fan unit having a depth such that the fanunit is spaced apart from the circuitry on the circuit module when thecircuit module and the fan module are mounted to different ones of thereceiving connectors.
 12. The fan module of claim 11 wherein theelectrical connectors are receiving connectors for optionally receivingthe circuit module board connector and the fan module board connector.13. The fan module of claim 11 wherein (1) the electronic system furtherincludes a housing, (2) the circuit module further includes a circuitmodule bracket assembly attached to the circuit module base board andattachable to the housing, and (3) the fan module further includes a fanmodule bracket assembly attached to the edge of the fan module baseboard and attachable to the housing interchangeably with the circuitmodule bracket assembly.
 14. The fan module of claim 11 wherein the fanmodule base board has an opening behind the fan unit through which anair flow is directed when the fan unit is operating.
 15. The fan moduleof claim 11 wherein the driving circuit has a noise filter for filteringpower transients on the driving circuit.
 16. The fan module of claim 11further including a light-indicator device for indicating that power forthe electronic system is on.
 17. The fan module of claim 11 wherein thefan unit is selectively mountable on the first and second planarsurfaces of the fan module base board.